Over the past decades, there have been a significant number of terrorists attacks on government buildings owned by the United States and other countries both outside of the United States and within. For example, in 1993, terrorists exploded a car bomb inside the garage of the World Trade Center located in New York City, resulting in loss of life and significant property damage. Since then, in 1995, other extremists exploded a truck outside of the Federal Building located in Oklahoma City, Okla. also resulting in significant loss of life and property damage. In 1998, the United States embassies in Nairobi and Dar Es Salaam were also subject to terrorists attacks by car bombs, each of which resulted in significant loss of life and property damages. More recently, the tragic events at the World Trade Center in New York City and the Pentagon in Virginia has further emphasize the long felt need to develop and manufacture building materials which are able to withstand the shock wave from car bomb explosions and other similar terrorist attacks.
Traditionally, the internal and external tiling of buildings, industrial and residential areas, government and private sector, etc., is commonly made of natural and artificial construction materials, the most used materials being cement, marble and granite, as well as ceramic tiles of various kinds. In addition to be decorative, the construction materials used should be functional, exhibiting the following characteristics: long durability, resistance to weather effects; resistance to corrosion; inert behavior to chemicals; thermal insulation properties; resistance to abrasion; and at the same time it should also be economical in both production and installation costs.
While the concept of using foam glass as a construction material is well known in the prior art, generally such foam glass has been used as a high temperature insulator and thus seeks to minimize its density and weight and is not suitable for absorbing sufficient energy from a shock wave from unexpected explosions or to resist an earthquake and/or wind and heat loading. The shortcomings in such conventional foam glass as relevant to this long standing problem are now described.
For example, Pittsburgh Corning Corporation (“PCC”) of Pittsburgh, Pennsylvania has developed and marketed a product known as Foam Glas® Insulation Systems, which is described in U.S. Pat. Nos. 3,959,541, 4,119,422, 4,198,224, 4,571,321 and 4,623,585. Because the focus of these developments are directed to making a foam insulating material, the Foam Glas® Insulation Systems tile commercially sold by PCC is relatively light, weighing 9.5 lb./cu. ft. Furthermore, since the purpose of this tile is to be used as thermal insulation, it lacks surface strength, and can be dented very easily. Because the Foam Glas® Insulation Systems tile is of relatively low density, e.g., 9.5 lb./cu. ft., such tiles will easily break when exerted to forces typically asserted on exterior walls to a building or other structure. Thus, such tiles are not suitable to be used as tiling for an exterior wall. Similarly, this foam, when exposed to a shock wave from an explosion will absorb very little of the shock waves energy when it implodes. A shock wave is a measure associated with explosions which is easily understood by those skilled in the art as being a pressure front resulting from an explosion.
Others have also attempted to use foam glass tiles as the outer skin-surface of buildings. For example, U.S. Pat. No. 5,069,960 discloses a thermally insulating foam glass tile that is coated with an outside surface to make a hard skin to protect the outside of a building. The tiles disclosed are fabricated in extremely small sizes, i.e., 18 cm×18 cm×6 cm, and the interior foam material which makes up the bulk of the material is generally of a low density. Significantly, there is no indication that the strength of the material disclosed is capable of absorbing sufficient energy from an explosion, and indeed the size of the disclosed tiles would not be ideally suitable for absorbing such energy. Furthermore, there is no indication that small size pores are being used.
Prior work by the inventors and others have developed methods for making foam glass tiles of a wide a variety of densities as described in U.S. Pat. No. 4,430,108 that can be used for building materials. While the techniques and methods disclosed were useful to manufacture then-standard size tiles of 4.25 in.×4.25 in.×0.25 in., this disclosure does not teach how to manufacture tiles of a larger size, for example 2 ft.×2 ft.×3 in. Likewise the tiles manufactured under these methods were relatively light, e.g., less than 10 lbs., and were not manufactured to withstand the effects of an explosion. To the contrary, these methods sought to optimize the thermal insulation properties of the material, and thus made smaller, lighter and weaker tiles.
While still others have worked on trying to make some large-size porous shaped bodies, these have been smaller in critical dimensions and of lower density than the present invention and not suitable to absorb a substantial amount of a shock wave which impacts the bodies associated with an explosion or earthquake. For example, U.S. Pat. No. 5,151,228 describes a process for manufacturing large-size porous shaped bodies of low density by swelling, in order to manufacture large-size cellular ceramic structural elements, e.g., multi-story high wall elements having a low weight. In the example, it discloses a tile 8.2 ft.×1.64 ft.×2 in., with a density of 26 lb./cu. ft. and a mass of 60 lbs. It also teaches to obtain a low density in order to optimize thermal insulation. Thus, this foam when exposed to a shock wave from an explosion or earthquake or heat or wind loading or stress of any kind will absorb very little of the shock waves energy when it implodes.
Further, others, such as Central Glass Co. Ltd., of Ube, Japan, have attempted to make foam glass using densities in the range of 0.3 to 0.6 g/cu. cm (or 18.7 to 37.4 lb./cu. ft.) as disclosed in U.S. Pat. No. 4,798,758. The '758 Patent explains that in order to make the foam glass stronger, an outer layer is also added which has a density in the range of 0.8 to 1.7 g/cu. cm and a thickness of 1.5 to 20 mm. In the examples shown, all the samples which are over 30 lbs. in weight were found to be unacceptable from a cutability and impact resistance perspective, for among other reasons that the surface had appreciable breaking and sometimes cracking, thus not providing a closed pore surface. Further, U.S. Pat. No. 4,833,015, a later patent by Central Glass Co. Ltd., explains the tensile strength perpendicular to the surface of the tile described in the '758 Patent was very poor, i.e., below 150 lb./sq. in., thus making it unsuitable for purposes of the present invention. Even after putting a third layer to improve the strength of the product as described in the '015 Patent, the best tensile strength achieved was below 200 lb./sq. in., and making it unsuitable for purposes of the present invention.
Other efforts by Central Glass Co., Ltd. attempt to make higher density glass tiles, such as U.S. Pat. No. 4,992,321. However, these tiles do not appear to be a closed pore structure and there is no indication as to their strength. Indeed, filler materials are used in an attempt to increase the strength with no reporting data. Further, the tiles disclosed were also very thin, 33 mm (or 1.3 in.).
Still others have attempted to make foam glass tiles with smaller pore size. For example, in U.S. Pat. No. 5,516,351, the relationship of pore size to thermal resitivity is shown in which the best pore size is always greater than 1.0 mm. Similarly, the density is always less than 12 lb./cu. ft. Other efforts to use small pore size and larger densities, such as U.S. Pat. Nos. 3,951,632 and 4,758,538, failed to achieve comparable strengths and does not disclose achieving a closed pore outer skin as disclosed by the present invention.
Unlike the prior art discussed above, the tiles of the present invention are designed and constructed of various materials so that such tiles have properties which are ideal for withstanding the shock wave associated with large explosions or make a building or other structure resistant to earthquakes.
Thus, while the prior art is of interest, the known methods and apparatus of the prior art present several limitations which the present invention seeks to overcome. In particular, it is an object of the present invention to provide a strong, high density foam glass tile with small average pore sizes which can be used as a building material.
It is another object of the present invention to increase from the commercially recommended density of 9.5 lb./cu. ft. to have a higher density of between 30-100 lb./cu. ft., and more particularly over 40 lb./cu. ft., and even more particularly over 60 lb./cu. ft.
It is another object of the present invention to make a foam glass tile with an average pore size of 1.0 mm or less, and more preferably of 0.6 mm or less, and even more preferably of 0.4 mm or less, and even more preferably of 0.3 mm or less.
It is a further object of the present invention to increase the weight of the foam glass tile to be greater than 30 lbs., and more particularly over 65 lbs. and even more particularly over 100 lbs.
It is a further object of the present invention to provide a strong, high density foam glass tile which can be used on the critical surfaces of buildings at high risk for terrorist attacks, in combination with cement, steel or other building materials.
It is also an object of the present invention to provide a glass foam tile that can be used in surfaces of typical buildings and has the advantage of having a rigid structure that when exposed to shock waves having blast energy, the tile can absorb a substantial portion of that blast energy. It also has the advantage of being more resistant to earthquakes and/or wind and heat loading.
These and other objects will become apparent from the foregoing description.